采用定长索设计的肋环型索穹顶结构索长误差影响的试验研究

Experimental study on the influences of cable length errors in Geiger cable dome designed with un-adjustable cable length

在国内建成的肋环型索穹顶结构中,多采用调节索长以控制结构性状(力态与形态)的施工方法,而国外更多采用定长索设计与施工。定长索设计是将索头设计为不能调节长度的形式,通过精确设计和控制各索的制作长度,在现场直接张拉到位,不需要反复调节索长,节省人力物力。使用定长索设计与施工,需要首先了解张拉结构中不同索的索长误差对其整体结构预应力态和荷载态的影响,进而依据相关理论确定索长误差控制值。文中针对索长误差的敏感性,设计一个平面为矩形的肋环型索穹顶结构模型,通过试验研究初始索长误差对预应力态的影响,比较不同索的索长误差影响范围及大小的不同,并试验初始索长误差影响与预应力水平的关系。在此基础上,通过试验研究不同荷载工况下初始索长误差对结构荷载态的影响,并进行对比。最后,比较预应力态不同,初始索长误差发生位置不同时,初始索长误差对荷载态的影响。研究成果对索穹顶结构的设计与施工张拉有指导作用。

In the construction of cable domes, design of cable with adjustable length is often adopted in China, while design of cable with un-adjustable length is often employed in other countries. In design of cable with un-adjustable length, cable ends are specially designed to be completely fixed so that cable length cannot be adjusted. The cable length must be designed accurately and manufactured according to the standards for the cable length, so that the cables can be directly and completely tensioned on site without the necessity of repeatedly adjusting cable length, leading to the savings in labors and costs. Obviously, the manufactural criteria of cable length shall be established when applying the design of cable with un-adjustable length, and the effects of cable length errors from tensioned structures on pre-stress states and loading states of global structure shall be understood. In this study, a cable dome structure with rectangular plane was designed and tested to study the influences of cable length errors. Firstly, the influences of cable length errors from different cables on pre-stress and loading states were investigated and compared, and then the relation between the initial cable length error and pre-stress level was explored. Furthermore, the influences of initial cable length errors on the loading states of dome structure under different loading cases were investigated experimentally. Eventually, when the pre-stress states are different and when the locations of cable length errors are different, the performance and responses of the cable dome structure were studied. The research results can provide guidance to the design and construction of Geiger cable domes.